This invention relates to a tube for a microscope having means for switching between different modes of operation, and having a diaphragm which covers the eyepiece viewer in the "photometry" or "photography" switch position. Such a tube is known, for instance, from Swiss Pat. No. 615,762 (Haas), issued 15 Feb. 1980, and from German Federal Republic patent application No. 3636616.1 The disclosures of those patents will serve as background for the present invention.
The diaphragm which is provided in the case of known photometer tubes has the object of preventing disturbing external light, which falsifies the photometric measurements, from entering the tube through the eyepiece viewer. Since the eyepiece viewer must be freed for entrance of light when a photometric visual observation of the object is to be made, the blocking diaphragm may be swung into and out of blocking position either manually by means of a suitable handle, or automatically by magnets when switching from one mode to the other, as described for example in the above mentioned patents.
Automatic switching by electromagnets or motors is disadvantageous in many cases, for instance when there is no room for such drives in the tube, or when the expense of electric drives is to be avoided.
The object of the present invention is to provide a tube of the above mentioned kind which has the simplest possible mechanical coupling between the external-light diaphragm and the switching means for switching or changing from one to another of the different modes of operation of the microscope.